Infrared heater



Feb. 20, 1968 J. .z. FANNON, JR.. ET A 3,369,536

lNFRA-RED HEATER Filed May 10, 1966 5 Sheets-Sheet l INVENTORS- JOHN J. FAN/VON, JR.-

MARC RESEK ATTORNEYS Feb. 20, 1968 J.J.FANNOII\J, JR. ETAL 3,369,536

INFRA-RED HEATER Filed May 10, 1966 5 sheets-sheet .lllllllll .lllllllll.

JNVENTORS JOHN J. FA/VNON, JR. BY MARC RESEK Wad/Q99? ATTORNEYS Feb. 20, 1968 J. J. FANNON, JR. ET AL 3,369,536

INFRARED HEATER Filed May 10, 1966 5 Sheets-Sheet 5 IN V EN TORS JOHN J. FANNON, JR BY MA RC RESEK 422a cflfi A 7'TOR/VEYS Feb. 20, 1968 .1. J. FANNON, JR. ET AL 3,369,536

INFRARED HEATER Filed May 10, 1966 5 Sheets-$heet 4 FIG. 4

JOHN J. FANNO/V, JR. BY MARC RESEK Feb. 29, 39%8 .1. a. FANNON, JR. ET AL INFHA-RED HEATER 5 Sheets-Sheet 5 Filed May 10, 1.966

s M M 5 RN v1 MOM M NN R E N E 0 WM 1 .0 WW R v A ,y J M 0m. v kw. m. NT

om m/ mm SM? 169 I Evy LII I I I I & J

3,369,536 INFRARED HEATER John J. Fannon, .Jr., Grosse Pointe Park, Mich., and Marc Resek, Shaker Heights, Ohio, assignors, by mesne assignments, to Fostoria-Fannon, Inc., a corporation of Ohio Filed May 10, 1966, Ser. No. 548,941 8 Claims. (Cl. 126-92) This invention relates to combustion type infrared generators and, more specifically, to improvements in the infrared generators disclosed in copending applications Nos. 395,839, filed Sept. 11, 1964, by John J. Fannon, Jr., for Apparatus and 397,775 filed Sept. 21, 1964, by John J. Fannon, J12, et al. for Apparatus, now Patent No. 3,305,241.

In the infrared generators disclosed in these copending applications, a fuel-air mixture distribution tube and a ribbon type orifice grid are employed to distribute the combustible mixture to a combustion zone adjacent the outlet ends of the ports formed by the ribbons in the orifice grid. A radiant grid surrounding the combustion zone is heated by the burning gases and converts the energy of the latter to radiant energy of Wave lengths suitable for object and area heating.

In these infrared generators, the orifice grids are clamped directly between flanges on the distribution tube which define an outlet passage from the distribution tube for the combustible mixture. Consequently, the outer ribbons and the tube flanges define ports through which the mixture can flow. This mixture burns at the outlet ends of these ports adjacent the tube flanges, heating the edges of the latter, particularly when 100% premixed air is employed as this produces a short sharp flame as opposed to a long lazy flame resulting when only a portion of the air is premixed with the fuel.

One of the advantages of the above-discussed infrared generators is that the distribution tube can be fabricated of inexpensive sheet metal such as aluminized steel. However, the passage defining flanges of such a distribution tube may be heated to a sufficiently high temperature to warp them by combustion adjacent the flanges as described above.

This warpage widens the ports between the outer ribbons and the flanges, permitting combustion to occur within the ports. Such combustion results in increased heating of the flanges and increased warpage. Consequently, the ports adjacent the flanges may become much larger than those in the grid. The combustible mixture flows at a higher rate through the enlarged ports, causing a higher rate of combustion at their outlet ends than elsewhere in the combustion zone, which results in uneven heating of the radiant grid. The uneven heating produces hot spots which materially shorten the life of the infrared generator.

This problem cannot be solved simply by making the distribution tube of a more heat resistant material. First, this solution is economically impractical. Also, particularly under severe operating conditions, the warpage described above may occur even though the distribution tube is fabricated from a more expensive and more heat resistant material.

We have now found, however, that warpage of the distribution tube flanges can be prevented by interposing strips of heat resistant metal between the flanges and the outer ribbons of the orifice grid. These strips keep the flanges away from the combustion zone, materially lowering the intensity of the heat to which the burner flanges are subjected.

Resistance to warpage may also be materially increased by clamping the flanges of the distribution tube between Patented Feb. 20, 1958 the heat resistant strips and the mounting legs of reflectors which perform the additional important function of reflecting the energy emitted from the sides of the radiant grids into the area or onto the objects to be heated. To further protect the distribution tube flanges from overheating, the outer edges of the flanges are preferably recessed in relation to the edges of the heat resistant strip and reflector mounting leg between which they are clamped. This arrangement keeps the edges of the flanges away from the combustion zone and the intense heat gen erated in this zone.

Another important feature of the present invention is the provision of novel reflectors of differing configurations which are intended to be used when the burners of the present invention are arranged in parallel spaced apart lines to project heat onto an extended surface. The reflector configurations are designed to provide uniform distribution of the radiant energy emitted from the infrared generators for various spacings of the burner lines. This use of reflectors of different configurations has been found to provide results superior to those obtained by employing reflectors with adjustable sides as has heretofore been proposed. It is generally impractical, in reflectors of the latter type, to make adequate provision for expansion and contraction or to provide a sufliciently rigid structure.

The reflectors of the present invention are also more effective than those heretofore known in protecting the radiant grid and distribution tube flanges from wind and air currents. Air moving across the radiant grid cools it, reducing the heat output of the infrared generator. And air moving across the flanges of the distribution tube blows the flame to one side, causing the combustion on the leeward side of the burner to be more intense than on the windward side. This causes uneven heating and consequent warpage of the radiant grid, which may become distorted to such an extent that it will tear loose from the clips by which it is supported.

By selection of the appropriate reflector configuration in accord with the present invention, the adverse effects of wind and air currents can be eliminated regardless of whether the air stream is blowing from the back of the burner, across its face, or directly toward its face.

This feature is particularly important in industrial applications involving the drying of granular materials or removal of moisture or solvents from plastic, paper, or other webs or from articles of various configurations since high velocity air is typically employed in such processes for ventilation and to carry olt fumes, vapors, and/or products of combustion. The reflectors of the present invention are also of particular importance in duct heater applications in which air for space heating is heated by blowing it across the burner at high velocity and in heaters for use out-of-doors or in drafty locations, where wind and air currents prevail.

Yet another novel feature of the infrared generators disclosed herein is the provision of improved, simplified arrangements for attaching the radiant and orifice grids and reflectors of the generator to its combustible mixture distribution tube and for attaching end plates to the radiant grids. These novel arrangements facilitate assembly of the infrared generators and removal of the reflectors, radiant grids, and orifice grids for servicing and replacement. Consequently, they significantly reduce the cost of manufacturing and maintaining infrared generators of the type to which this invention relates.

One important and primary object of this invention resides in the provision of novel, improved infrared generators of the type disclosed in copendin-g applications Nos. 395,839 and 397,775.

Other important but more specific objects of the present invention include the provision of infrared generators in accord with the present invention:

(1) In which the flanges forming the outlet passage from the combustible mixture distribution tube are protected from overheating to prevent warpage and the consequent formation of hot spots which would shorten the life of the infrared generator.

(2) In which, in conjunction with the preceding object, strips of heat resistant material are interposed between the distribution tube flanges and the outer ribbons of an orifice grid in the distribution tube outlet passage to protect the flangesof the distribution tube.

(3) In which, in conjunction with objects 1) and (2), the distribution tube flanges are clamped between the heat resistant strips and the mounting legs of radiation directing reflectors incorporated in the infrared generators to stiffen the flanges and thereby protect them against warpmg.

(4) In which, in conjunction with objects (1-3), the edges of the distribution tube flanges are recessed relative to the heat resistant strips and reflector legs to increase the protection against overheating afforded by the latter.

(5) Which may be readily utilized in multiple side-byside lines having different spacings and which will provide a substantially uniform distribution of emitted energy regardless of the spacing.

(6) Which will operate properly in industrial applications, as duct heaters, as radiant heaters in out-of-door and drafty locations, and in other environments in which they are contacted by wind or other air currents.

(7) Which, in conjunction with the preceding object, are not susceptible to wind or air currents regardless of whether the air is moving from the back of the burner, across the face of the burner, or toward the face of the burner.

(8) Which are simpler and less expensive to assemble, manufacture, and maintain than the infrared generators of this general type heretofore available.

(9) Which, in conjunction with the preceding object, have a novel, improved and simplified arrangement for fixing the radiant and orifice grids and reflectors to the distribution tube of the infrared generator which facilitates the assembly and removal, and replacement of these components.

(10) Which, in conjunction with objects (8) and (9), have an improved arrangement for fixing the grid supporting end plates to the radiant grids of the infrared generators.

A further important and specific object of this invention is the provision of novel, improved reflectors for infrared generators of the type disclosed herein, which have different configurations such that the reflectors may be utilized to vary the spacing between generators in multiple line installations without affecting the uniformity of radiant energy distribution and which may be used to protect the generator from the effects of wind and air currents moving in different directions in relation to the face of the infrared generator.

Other objects, additional novel features, and further important advantages of the present invention will become apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIGURE 1 is a fragmentary side view, partly in sec-.

tion, of a combustion type infrared generator constructed in accord with the principles of the present invention;

FIGURE 2 is a fragmentary section through the infrared generator of FIGURE 1;

FIGURE 3 is a section through the infrared generator of FIGURE 1, taken substantially along line 33 of the latter figure;

FIGURE 4 is a fragmentary bottom view of the infrared generator of FIGURE 1;

FIGURE 5 is a section through a radiant grid em- 4 ployed in the infrared generator of FIGURE 1, taken substantially along line 55 of the latter figure;

FIGURE 6 is a perspective view of a radiant grid supporting clip employed in the infrared generator of FIG URE 1;

FIGURE 7 is a perspective view of one form of reflector assembly which may be employed in the infrared generator of FIGURE 1;

FIGURE 8 is a view similar'to FIGURE 3, showing a second form of reflector assembly;

FIGURE 9 is a view similar to FIGURE 3, showing a third form of reflector assembly;

FIGURE 10 is a view similar to FIGURE 3, showing a fourth form of reflector assembly;

FIGURE 11 is a view similar to FIGURE 1 of a second form of infrared generator constructed in accord .with the principles of the present invention;

FIGURE 12 is a view of the infrared generator of FIGURE 11, looking in the direction of arrows 12-12 in the latter figure;

FIGURE 13 is a section through the infrared generator of FIGURE 11, taken substantially along line 13--13 of the latter figure;

FIGURE 14 is a section through a radiant grid employed in the infrared generator of FIGURE 11, taken substantially along line 14-14 of the latter figure;

FIGURE 15 is a perspective view of a grid supporting clip employed in the infrared generator ofFIGUREll; and

FIGURE 16 is a fragmentary end view of a second form oforifice grid which may be used in the infrared generators of FIGURES 1 and 11.

Referring now to the drawing, in which exemplary embodiments of the present invention are shown, FIGURE 1 depicts an infrared generator 20 constructed in accord ance with the principles of the present invention. Infrared generator 20 includes a fuel-air mixture distribution tube 22; an orifice grid 24, through which the fuel-air mixture flows from the interior of distribution tube22 to a combustion zone 25 adjacent the outer end or face 26 ,of the grid; radiant grids 28, which are heated to incandescence by the combustion of the fuel-air mixture; reflectors 30 for concentrating the radiant energy emitted by radiant grid 28 and projecting it in the desired direction .or directions (the infrared generator may be disposed in any orientation desired for a particular application); and endv brackets 32 and 33 which form closures for the open ends of distribution tube 22 and by which infraredgenerator 20 is attached to a supporting frame 34 shown diagrammatically in FIGURE 1.

Referring now to FIGURES 1-4, distribution tube 22 is formed from sheet metal (aluminized sheet steel is satisfactory) into a generally diamondlike configuration defined by four side walls 36. As is best shown in FIG- URE 3, the opposed lateral edge portions of the sheet from which'distribution tube 22 is formed are bent at angles to the two distribution tube walls 36 with which they are integral to form two parallel, spaced apart flanges 38. These flanges provide an outlet passage from the interior to the exterior of the distribution tube.

Orifice grid 24, through which the combustible fuelair mixture flows from distribution tube 22, is mounted in the outlet passage'40 of a fuel-air mixture distribution tube 22 to distribute the combustible mixture uniformly over combustion zone 25 and to prevent the flame from flashing back from the combustion zone through passage 40 to the interior of distribution tube 22. The illustrated orifice grid 24 is of the ribbon type (it is not critical that a ribbon type orifice be employed) and consists of embossed metallic ribbons which provide a number of small passages extending between and opening onto the opposed lateral edges of the assemblage of ribbons. The particular configuration of the individual ribbon is not critical in the present invention; and the length and total area of the lateral passages may be varied as desired for particular applications of this invention. It is necessary, however, that the lateral passages be sufliciently small in cross section and sufficiently long that flame cannot flash back through the passages from combustion zone to the interior of distribution tube 22. In addition, the total area of the openings must be great enough that the combustible mixture will flow from distribution tube 22 to the combustion zone in sufficient quantity to maintain the desired rate of combustion.

One particular type of orifice grid structure, which functions particularly well, is illustrated in FIGURE 4. This grid structure 24 is formed from metallic ribbons 42 in which laterally extending triangular convolutions 44 are formed at periodic intervals. Ribbons 42 are assembled in pairs with the two ribbons in each pair disposed in mirror image relationship. The pairs of ribbons are assembled in side-by-side relationship with the convolutions 44 of one pair of ribbons midway between the convolutions 44 of the adjacent pair. The ribbons 42 are pinned or brazed together at opposite ends of the grid structure to give the latter structural integrity.

This arrangement provides lateral passages 46 between the associated convolutions 44 of the two ribbons in each pair and lateral passages 48 which are defined by the juxtaposed convolutions 44 of ribbons in adjacent ribbon pairs and the portions of the juxtaposed ribbons in adjacent pairs intermediate the convolutions. There are also lateral passages 50 between the outermost ribbons 42 and strips 52 of heat resistant metal interposed between the outermost ribbons 42 and distribution tube flanges 38 to stiffen the latter and to protect them from the heat generated in combustion zone 25. As discussed above, this arrangement is an important feature of the present invention because it helps to prevent warpage of the flanges and, therefore materially increases the service life of the type of infrared generator disclosed herein.

Orifice grid 24 is removably retained in outlet passage 40 between distribution tube flanges 38 by studs 54 (see FIGURE 3). Studs 54, which extend laterally through distribution tube flanges 38 at spaced intervals therealong,

locate orifice grid 24 relative to the inner end 56 of paw sage 4t). Retainers 58, threaded on the ends of studs 54, clamp flanges 38 against orifice structure 24 to removably retain it in passage 40.

Radiant grids 28, which are heated toincandescence by the combustible mixture flowing through orifice structure 24 and burning adjacent its outer face 26 and emit the radiant energy desired for space, article, or other heating in radiant energy applications of this invention, may be of the apertured construction disclosed in the copending applications referred to above although it is not necessary that this particular type of radiant grid be employed. Each grid 28 is made of a sheet of heat resistant metal such as Inconel or Hastelloy-X or a coated alloy bent into a horseshoe configuration providing a radiation emitting body 68 and inturned mounting flanges 62.

As best shown in FIGURES 2 and 3, the body 60 of each radiant grid 28 is formed into a configuration in which circumferential rows of ribs or loops 64 are displaced from the sheet from which the grid is formed at regular intervals to form openings extending normal to the sheet through which the combustion products may pass from the combustion zone. Successive loops 64 in each row are alternatively displaced toward the inside and outside of the grid, and successive rows of loops are displaced longitudinally along the grid. These loops in the circumferential rows of loops may also be spaced circumferentially to form longitudinal rows of loops as shown in FIGS. 1, 12 and 13. As discussed in detail in copending application No. 395,839, this results in a grid which is a highly efficient emitter of infrared radiation and which effectively protects the flame from air currents of sufiicient strength to quench or snuff it out. In flanges 62, loops 64 are flattened back into the plane of the flanges or are omitted to provide flat flanges which can be readily 6 clamped between the members employed attach grid 28 to distribution tube 22.

Referring now specifically to FIGURES 2 and 5, end plates 66 are disposed between two circumferential rows of loops 64 at the ends of grids 28 and secured in place by ears 68 bent from the grid and fixed as by welding to the end plates. End plates 66 support the open ends of each grid 28 and maintain the body of the grid in the desired shape. They also prevent air currents from disturbing the flame. If desired, an aperture 70 may be provided in the right'hand end plate 66 to facilitate lighting of the infrared generator or to accommodate a spark plug or flame sensor. Apertures (not shown) may also be provided in the juxtaposed end plates of adjacent grids to allow flame to travel from one radiant grid to the next.

The method of attaching end plates 66 to radiant girds 28 just described is an important feature of the present invention. As only two spot welds are needed to fasten each end plate in position, this method materially reduces the cost of producing the grids from that of producing similar structures by previously known techniques.

Radiant grids 28'are removably attached to the flanges 38 of distribution tube 22 by one-piece grid clips 72, which also assist in retaining orifice grid 24 in its proper position in the outlet passage 40 between the flanges.

Referring now to FIGURES 1, 3, and 6, the clips 72 employed in infrared generator 20 to support radiant grid 28 are formed of temperature resistant sheet metal and have a main body portion, three inner rectangular legs 76, 78, and 80, which extend at right angles from clip main body portion 74, and two outer rectangular legs 82 similarly disposed relative to the main body portion. Inner legs 76 and lie in the same plane; and leg 78 lies in a plane spaced from leg 76 and 80.

Radiant grid supporting clips 72 are fixed in back-toback relationship to the two flanges 38 of distribution tube 22 at locations corresponding to the ends of radiant grids 28 by the previously discussed studs 54, which extend through apertures 86 in the main body portions 74 of the clips, and retainers 58, which clamp clips 72 against the flanges 38 of distribution tube 22. Studs 54 will typically be spaced three inches apart although this spacing may be varied as desired. Rectangular washers having the same thickness as clip bodies 74 are disposed on the studs 54 on which there are no clips between each of the distribution tube flanges 38 and the juxtaposed retainer 58. This insures proper clamping of the distribution tube flanges and heat resistant strips 52 against orifice grid 24 at each of the stud locations.

As is best shown in FIGURE 3, inner legs 76 and 80 of each clip 72 engage one surface of the associated flange 62 of radiant grid 28 and the central inner clip leg 78, the opposite surface of the associated flange, thus supporting radiant grid 28 from fuel-air mixture distribution tube 22. The distance between the two sets of grid clip legs is preferably slightly greater than the thickness of flanges 62. This permits longitudinal movement of flanges 62 between the legs of the clips as the parts expand and contract due to temperature changes, but restrains flanges 62 and the body of grid 28 from appreciable transverse movement. This permits grid 28 to expand axially as the temperature increases, which prevents it from becoming distorted as it expands and contracts longitudinally. Lateral expansion is accommodated by the horseshoe configuration of the grid.

The two outer legs 82 of each clip 72 support the outer end 26 of orifice grid 24, preventing it from dropping out from between distribution tube flanges 38, but permitting it to be slid lengthwise of the distribution tube to remove it from infrared generator 20.

Any number of radiant grids may be mounted in end-toend relationship in this fashion, the number of grids depending primarily on the length of infrared generator 20. It is preferred, however, that the length of the grids be limited to 12-18 inches. Otherwise, undue distortion may result because of the large differential between operating and nonoperating temperatures and, consequently, the high degree of expansion and contraction of the grid during cycling of the infrared generator.

Referring now to FIGURES 1 and 3, each of the two reflectors 30 of infrared generator consists of a first reflecting leg 92, a second reflecting leg 94, and a mounting leg 96, by which the reflector is fixed to the fuel-air mixture distribution tube 22 of infrared generator 20. The configuration of reflector illustrated in FIGURE 3 is particularly suited for illustrations in which plural infrared generators are mounted in side-by-side relationship in multiple lines with the distance between adjacent lines being about eight inches or less. To suit them for such installations, reflecting leg 94 is formed at generally a right angle to mounting leg 96, and reflecting leg 92 is formed at an angle of at least 45 degrees to reflecting leg 94.

As shown in FIGURE 1, reflectors are approximately the same length as radiant grids 28 and are assembled to distribution tube 22 in end-to-end relationship with gaps 98 (see FIGURE 7) between adjacent reflectors to accommodate expansion of the reflectors during operation of infrared generator 20.

Reflectors 30 are fixed to distribution tube 22 by the studs 54, mentioned above, which extend through apertures 100 in mounting legs 96, and by retainers 58, which clamp mounting legs 96 against distribution tube flanges 38. This relationship of reflector mounting legs 96 to distribution tube flanges 38 is an important feature of the present invention since the reflector mounting legs protect the distribution tube flanges against the heat generated in combustion zone 25 and materially stiffen them, further the edges of flanges 38 from the heat generated in com- 7 bustion zone25, further minimizing warpage of the distribution tube flanges. This novel arrangement, together with the stiffening of the flanges provided by heat resistant strips 52 and reflector mounting legs 96, virtually eliminates warpage of the distribution tube flanges as a problem. Therefore, distribution tube 22 may, as discussed above, be made of a relatively inexpensive sheet metal without shortening the service life of the infrared generator. Thus, the foregoing arrangement materially reduces the cost of manufacturing and using infrared generators of the combustion type.

In employing infrared generators of the type disclosed in this application in environments in which there is air of appreciable velocity, openings in the reflectors on the windward side of the infrared generator must be eliminated to prevent air currents from passing through gaps between the reflectors and disturbing the flame in combustion zone 25. To accomplish this goal, the gaps 98 between adjacent reflectors 30 are covered by shields 102 (see FIGURE 7), which have a main body portion 104 with the same configuration as the reflecting portion of reflectors 30 and a flange 106, at the bottom of body portion 104. The flange 106 aligns the lower edges of the reflecting legs 92 of adjacent reflectors.

Shields 102 extend across gaps 98 and are fixed to one of the two adjacent reflectors 30 on opposite sides of the gap as by spot welds 108. The shields are left free of connection to the other of the two adjacent reflectors to accommodate expansion and contraction of reflectors 30 during cycling of the infrared generator.

Referring now to FIGURES 1-3, sheet metal end brackets 32 and 33 are provided for closing the ends of fuel-air mixture distribution tube 22 and for securely attaching infrared generator 20 to its supporting structure 34, as mentioned above.

End bracket 32 has two integral legs 114 and 116, bent at right angles into an L-shaped configuration. With end bracket 32 assembled to distribution tube 22 (see FIGURE 2), bracket leg 114 is juxtaposed to and forms a closure for the open right-hand end of distribution tube 22. Bracket leg 116 extends along the top of distribution tube 22 in parallel, spaced relationship to the intersection 118 between the two upper walls 36 of the distribution tube.

As best shown in FIGURES 2 and 3, two cage nuts 120 are welded in side-by-side relationship to the bottom side of bracket mounting leg 116; and cooperating apertures 122 are formed in mounting leg 116 in alignment with the threaded central bores 124 of the cage nuts. By this novel arrangement, the right-hand end of infrared generator 20 may be readily and securely attached to the diagrammatically illustrated supporting frame 34 merely by threading the bolts 126 passing through the frame into cage nuts 120. As shown in FIGURE. 1, this clamps bracket mounting leg 116 against supporting frame 34 to rigidly secure the right-hand end of infrared generator to the frame.

Referring now to FIGURES 1 and 2, an aperture lZS 1 is formed inbracket leg 114 to accommodate a combustile mixture supply conduit 130. This conduit extends from the source of the combustible mixture (which is not shown, butmay be, for example, a fuel-air mixer) into the interior of the fuel-air mixture distribution tube.

The end bracket 33 employed at the left-hand end of fuel-air mixture distribution tube 22 is identical to end bracket 32 except that there is generally no combustible mixture supply conduit at this end of distribution tube 22, and, therefore, no aperture 128 in bracket 33. End bracket 33 supports the left-hand, end of, infrared generator 20 from support 34 in the same manner that bracket 32 supports its right-hand end.

End brackets 32 and 33 are attached to fuel-air mixture distribution tube 22 by angle clamps 132 which are best illustrated in FIGURES 1 and 3 and which are fixed in pairs to each end of tube 22. Each of the angle clamps 132 includes a clamping leg 134 and a base 136 bent, midway between its ends, to abut adjacent upper and lower walls 36 of distribution tube 22.

Angle clamps 132 are fixed to distribution tube 22 as by spot welding their bases 136 to side walls 36. The two angles clamps 132 at each end of fuel-air mixture distribution tube 22 are aligned transversely of the distribution tube so that the clamping legs 134 of the two angle clamps lie in the same transverse plane.

The mounting legs 116- of end brackets 32 and 33 are fixed to the clamping legs 134 of the angle clamps at their respective ends of fuel-air mixture distribution tube 22 by bolts 138, which extend through the end brackets and angle clamps. Nuts 142, threaded on bolts 138, clamp end brackets 32 and 33 against the angle clamps.

Referring now to FIGURES 1 and 2, to prevent the combustible mixture from leaking from the ends of fuelair mixture distribution tube 22, gaskets 144 (only one of which is shown) are assembled between the closure forming legs 114 of end brackets 32 and 33 and the associated ends of distribution tube 22. When bolts 138 are tightened, gaskets 144 are compressed and form gas tight seals between the ends of the distribution tube and the associated closure forming legs 114 of the two end brackets.

A central aperture 148 is formed in the right-hand movement toward and away from distribution tube 22. The closure forming leg 114 of bracket 33 is preferably constructed in a similar manner to provide a support for the orifice grid at the left-hand end of the generator.

Many modifications of the exemplary line burnerinfrared generator embodiment just described may, of course, be made within the scope of the present invention. For example, by varying the configuration of the reflector employed, infrared generator 20 may be readily adapted for use in multiple line installations in which there is either a greater or smaller spacing between lines than those for which the reflectors 30 illustrated in FIG- URE 3 are intended. Specifically, where the spacing between adjacent lines is eight inches or more, reflectors 152 with the configuration shown in FIGURE 8 may be employed to insure substantially uniform distribution of radiant energy over the area covered by the multiple generator lines. Reflectors 152 are similar to reflectors 30 except that there is only a small angle between the reflecting legs 154 and 156 of the latter instead of the 45 degree or greater angle between the reflecting legs of reflector 30. This reflector configuration allows the radiant energy emitted from each line to cover a wide span and overlap the beam of radiant energy projected from adjacent lines, providing substantially uniform and complete coverage over an extended surface.

Similarly, for installations where adjacent burner lines are relatively close (for example, on three inch centers), the reflectors 158 illustrated in FIGURE 9 are preferably employed to insure complete and substantially uniform coverage. Reflectors 158 are also similar to reflectors 30 except that the angle between reflecting legs 160 and 162 of reflectors 158 approaches a right angle; and the reflecting legs 162 extend from the level of the distribution tube well past the radiant grid of the infrared generator in which they are incorporated.

Also, by modifying the configuration of the reflectors employed, the infrared generators disclosed herein may be readily adapted for use in environments in which high velocity air currents are present. Specifically, where the infrared generators are located in air streams blowing laterally across the infrared generator from one side as indicated by arrows 164 in FIGURE 10, reflectors 166 and 168 with the configuration illustrated in this figure are preferably employed, reflector 166 being disposed on the leeward side of the infrared generator and reflector 168 on its windward side.

The leeward side reflector 166 may be identical to the reflectors 158 described above in conjunction with FIGURE 9.

Reflector 168 is similar to reflector 166 except that reflecting leg 170 of the latter is much longer than the corresponding reflector leg or reflector 166 and terminates in an inwardly directed edge portion 172 at its free edge. This arrangement has been found highly effective for deflecting moving air away from the radiant grids, providing good performance in environments in which there were laterally moving air streams having velocities of over 2500 feet per minute. Infrared generators with reflectors of the type illustrated in FIGURE are therefore admirably suited for use in applications such as industrial ovens of certain types in which air moving at such velocities is employed.

Reflectors having the various configurations discussed above in conjunction with the embodiments of FIGURES 1-10 are also highly effective in deflecting away from the radiant grids of the infrared generators in which they are incorporated wind and air currents moving toward the face of the generator as shown by arrows 174 in FIG- URE 3. Therefore, infrared generators equipped with reflectors of the type disclosed herein are well suited for use in applications in which there are air currents moving in such relation to the radiant grids.

Still other modifications of the infrared generator 176 illustrated in FIGURES 11-15. Referring now to the latter figures, infrared generator 176 differs from infrared generator 20 primarily in the structure of its radiant grids and in the components provided for assembling the radi ant grids to the remainder of the infrared generator. To the extent that the two infrared generators are the same, they have been identified by like reference characters.

Referring now specifically to FIGURE 11, infrared generator 176 employs three radiant grids 28a, 28b, and 28c assembled in end-to-end relationship. Only the ends of radiant grid 28a adjacent end bracket 33 and 280 adjacent end bracket 32 are provided with end plates, these being identified by reference character 178 in FIGURE 11.

Referring now to FIGURE 14, end plates 178, which are typically fabricated of 0.030 inch Inconel or similar heat resistant metal, have a main body portion 180 from which two ears 182 project. An aperture 184 of any suitable size or shape may be provided in end plate body 180 to facilitate lighting of the infrared generator or to accommodate a spark plug or flame sensor (not shown).

End plates 178 are attached to the radiant grids 28 with which they are associated in the same manner as the end plates 66 discussed above in conjunction with the embodiment of FIGURE 1.

In infrared generator 176, the ends of radiant grids 28a and 28c to which the end plates are assembled are supported from brackets 33 and 32, respectively, as by sheet metal screws 186 (see FIGURE 11). With the end plates thus assembled to the end brackets, orifice grids 24 extend through square notches 188 in the end plates.

Referring now to FIGURES 1113 and 15, U-shaped clips 190 support the ends of radiant grids 28a and 280 opposite end plates 178 and both ends of radiant grid 28b from the two reflectors 158 incorporated in infrared generator 176. Each of the clips 190 has a base 192 and two notched lugs 194 extending normally from the base at opposite ends thereof. A centrally located aperture 196, formed in the clip base 192, permits the combustible mixture to flow from orifice structure 24 through the clip to combustion Zone 25.

As is best shown in FIGURE 13, the base 192 of each clip 190 is fixed, as by welding at 197, to the mounting flanges 62 of the associated radiant grid 28. The clips therefore perform the function of maintaining the radiant grids in the desired shape or configuration.

Referring now to FIGURES 11 and 13, the lugs 194 of mounting clips 190 extend through elongated slots 198 in the reflecting legs 160 of reflectors 158. The projecting portions 200 of lugs 194 engage reflecting legs 160 adjacent the ends of slots 198, laterally positioning the ends of the radiant grids to which they are attached relative to the reflectors and the components of the infrared generator to which the reflectors are attached. At the same time, the elongated slots accommodate longitudinal movement of clips 190. Therefore, grids 28a and 280 are free to expand and contract longitudinally during the cycling of infrared generator 176.

In the case of radiant grid 28b, a sheet metal screw 202 or other fastener is employed to fix mounting flanges 62 to reflector legs 160 at approximately the middle of the grid. This permits expansion and contraction of grid 28b but, at the same time, prevents the grid from shifting to the extent that projecting lu-g portions 194 of clips 190 can drop through the slots 198 in the reflector legs.

By mounting radiant grids 28 in the manner described above, the use of radiant grid clips of the type disclosed in conjunction with the embodiment of FIGURE 1 and in copending application No. 397,775 is eliminated. This provides a number of important practical advantages. First, radiant grids can be removed for servicing or replacement without removing the studs on which the clips of the type just mentioned are supported. This reduces the time and, therefore, the cost of servicing the infrared generator. Second, bolts can be substituted for the studs necesarily employed with the latter type of clips and as- 1 1 sembly of the unit is more rapid, factors which are important in reducing manufacturing costs.

Third, the possibility of warpage is reduced because the radiant grids have greater freedom to expand and contract during cycling of the infrared generator. Fourth, the end of radiant grid 28c adjacent the fuel-air mixture supply conduit (not shown in FIGURE 11), to which end plate 178 is attached, is positively positioned relative to the end of distribution tube 22. This facilitates ignition of the infrared generator, particularly where a spark plug is used as the igniter.

The grid mounting arrangement just described is not limited to infrared generators employing three radiant grids. For aninfrared generator with a single radiant grid, the grid would be constructed and assembled in the manner of radiant grid 28a. Similarly, with an infrared generator employing two radiant grids, the grids would be identical and assembled in the same manner as radiant grids 28a and 280 in FIGURE 11. For infrared generators with more than three radiant grids, the additional grids would be identicalto the grid 28b of FIGURE 11.

Referring now to FIGURES l2 and 13, the reflectors 158 incorporated in infrared generator 176 differ from the reflectors 158 illustrated in FIGURE 9 in that their reflecting legs 160 extend in closely spaced relationship past the sides of the radiant grids and then diverge away from the radiant grids at a small anglehThis form of reflector has been found to be particularly advantageous for infrared generators employed as out-of-door space heaters. Any of the other forms of reflectors disclosed herein or such other forms as may be desired may of course be substituted for that shown in FIGURES 12 and 13, if desired.

To further illustrate the type of modifications which may be made in the exemplary embodiments of the present invention discussed above without exceeding the scope of the invention, a second form of orifice grid 204,which may be used in any of the infrared generator embodiments discussed previously, is illustrated in FIGURE 16,. Turning now to the latter figure, orifice grid 204- is formed from metallic ribbons 206 in which laterally extending semicircular convolutions 208 are formed at periodic intervals. In the illustrated orifice grid 204, six such ribbons are employed. The four innermostribbons 206 are assembled in pairs with the two ribbons in each pair being disposed in mirror image relationship. The two pairs of ribbons thus provided are assembled in side-by-side relationship with the convolutions 208 of one pair approximately midway between the convolutions 208 of the other pair. The remaining ribbons 206 are assembled in mirror image relationship on opposite sides of the two pairs of ribbons just described. The six ribbons 206 are pinned or brazed together at opposite ends of the grid structure to give the latter structural integrity.

This arrangement provides lateral passages 210 between the associated convolutions 208 of the ribbons 206 in the two inner pairs and lateral passages 212, which are defined by the juxtaposed convolutions of ribbons in adjacent pairs and the portions of the juxtaposed ribbons in adjacent pairs adjacent the convolutions. The ribbons similarly define-passages 214 between the ribbons 206 in the two inner pairs and the two outer ribbons 206 and passages 216 between the outer ribbons and the strips 218 of heat resistant metal interposed between the orifice structure and distribution tube flanges 220.

From the foregoing, it will also be apparent that many other modifications in the exemplary embodiments of the invention described above may be made without exceeding the scope of the present invention. To the extent that such modifications and improvements may be made without exceeding the scope of the present invention, they are fully intended to be covered by the appended claims unless expressly excluded therefrom.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. In an infrared generator of the combustion type:

(a) a fuel-air mixture distribution tube having opposed spaced longitudinal flanges forming a passage communicating between the interior and the exterior of the distribution tube;

(b) an orifice structure between said flanges in said passage for distributing fuel-air mixture from said tube to a combustion zone adjacent the outer end of the passage formed by the flanges of said tube and for preventing flashback from said combustion zone through said passage to the interior of the distribution tube; and

(c) a radiant grid configured to surround said combustion zone and adapted to be heated by burning of the fuel-air mixture therein;

(d) said orifice structure extending beyond the free edges of said opposed flanges so as to maintain said free edges out of the zone of intense combustion;

(e) reflectors having spaced longitudinal mounting flanges attached to the outside of said opposed flanges;

(f) means extending through all of said flanges for supporting said orifice structure and said reflectors to the distribution tube; and

(g) means for supporting said grid from said reflectors.

2. An infrared generatoraccording to claim 1 wherein said reflectors are disposed on opposite sides of said radiant grid for concentrating the radiant energy emitted from said grid and directing it in the desired direction, said reflectors having reflecting legs extending from the level of the distribution tube, past said radiant grid, the reflecting leg of one of said reflectors extending well beyond said grid and having an inturned edge portion for directing wind and aircurrents away fro-m said grid, said reflectors thereby adapting said infrared generator for use in an environment in which there is high velocity air moving laterally relative to the infrared generator.

3. The infrared generator of claim 1, with strips of heat resistant material between said orifice structure and each of said opposed flanges, said strips being substantially coextensive in length with said orifice structure and extending beyond the free edges of the opposed flanges the same distance as the orifice structure.

4. In an infrared generator of the combustion type:

(a) a fuel-air mixture distribution tube;

(b) an orifice structure for distributing a fuel-air mixture from said tube to a combustion zone adjacent said tube and for preventing flashback from said combustion zone to the interior of the tube;

(c) a radiant grid configured to surround said com: bustion zone and adapted to be heated by the burning of the fuel-air mixture therein, said grid having circumferential rows of ribs formed therein with adjacent ribs in each row being displaced toward, the inside and the outside of the grid, respectively;

(d) an end plate atat least one end of the grid to close said end and to retain the grid in the configuration to which it is formed, said end plate being disposed between two rows of said ribs at the end of the grid; and

(e) ears bent from said grid and fixed to said end plate to retain it betweensaid rows of said ribs.

5. The infrared generator of claim 4:

(a) wherein said radiant grid has mounting flanges (62) on the sides thereof, and

(b) said distribution tube has opposed flanges (38) forming a passage communicating between the interior and the exterior of the distribution tube, said orifice structure (24) being disposed in said passage between said flanges, and including (c) clips (72) for fixing each of said mounting flanges (62) to said distribution tube and for retaining said orifice structure between the passage defining flanges (38) of the distribution tube, said clips being spaced along said passage defining flanges on both sides thereof with each clip including a plurality of projections, different ones of said projections being adapted to abut said orifice structure to retain it between the flanges of the distribution tube, and

(d) studs (54) extending through said clips and the flanges of the distribution tube and fixing said clips to said flanges.

6. In an infrared generator of the combustion type:

(a) a fuel-air mixture distribution tube;

(b) an orifice structure for distributing a fuel-air mixture from said tube to a combustion zone adjacent said tube and for preventing flashback from said combustion zone to the interior of the tube;

(c) a radiant grid configured to surround said combustion zone and adapted to be heated by the burning of the fuel-air mixture therein;

(d) reflectors disposed on opposite sides of said radiant grid for concentrating the radiant energy emitted by said grid and directing it in the desired direction;

(e) end plates fixed to one end of said distribution tube and to the adjacent end of said radiant grid to seal the open ends of said distribution tube and said radiant grid, respectively; and

(f) means for supporting said grid relative to said distribution tube including means fixing said radiant grid end plate to said distribution tube end plate to positively position one end of said grid relative to said distribution tube, the other end of said grid being movable longitudinally of said distribution tube to accommodate expansion and contraction of said grid during cycling of the infrared generator.

7. In an infrared generator of the combustion type:

(a) a fuel-air mixture distribution tube;

(b) an orifice structure longitudinally of said tube for distributing a fuel-air mixture from said tube to a combustion zone adjacent said tube and for preventing flashback from said combustion zone to the interior of the tube;

(c) a radiant grid configured to surround said combustion zone and adapted to be heated by the burning of the fuel-air mixture therein;

(d) reflectors disposed on opposite sides of said radiant grid for concentrating the radiant energy emitted by said grid and directing it in the desired direction; and

(6) means for so attaching said radiant grid to said reflectors on opposite sides of said radiant grid so as to permit relative longitudinal movement therebetween and thereby accommodate expansion and contraction of said grid during the operation of said infrared generator, said attaching means comprising members fixed to said grids, each member having lugs extending through slots in the reflectors, said slots being longer than the portions of the lugs extending therethrough to permit movement of said grid longitudinally of said reflectors.

8. The infrared generator of claim 7, together With means fixing one end of said grid relative to said reflectors.

References Cited UNITED STATES PATENTS 1,909,496 5/1933 McKee 158-116 1,933,318 10/1933 Doen 158116 2,417,606 3/1947 Mitchell et al. 15899 2,427,892 9/1947 Adams 158-99 2,443,101 6/1948 Flynn et al 158116 2,543,688 2/1951 De Coriolis et a1. 15899 2,766,819 10/1956 Little 158113 2,884,998 5/1959 Taylor 158116 2,980,104 4/1961 Patrick et al 126271.2 3,139,881 7/1964 Fannon 12692 3,169,572 2/1965 Constance et a1. 158116 3,199,570 8/1965 Williams et al. 158-104 3,202,205 8/1965 Webster 12692 3,233,653 2/ 1966 Nakamura et al 126-92 FOREIGN PATENTS 448,960 6/ 1948 Canada.

450,550 7/1936 Great Britain.

805,614 12/1958 Great Britain.

904,792 8/ 1962 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner. 

1. IN AN INFRARED GENERATOR OF THE COMBUSTION TYPE: (A) A FUEL-AIR MIXTURE DISTRIBUTION TUBE HAVE OPPOSED SPACED LONGITUDINAL FLANGES FORMING A PASSAGE COMMUNICATING BETWEEN THE INTERIOR AND THE EXTERIOR OF THE DISTRIBUTION TUBE; (B) AN ORIFICE STRUCTURE BETWEEN SAID FLANGES IN SAID PASSAGE FOR DISTRIBUTING FUEL-AIR MIXTURE FROM SAID TUBE TO A COMBUSTION ZONE ADJACENT THE OUTER END OF THE PASSAGE FORMED BY THE FLANGES OF SIAD TUBE AND FOR PREVENTING FLASHBACK FROM SAID COMBUSTION ZONE THROUGH SAID PASSAGE TO THE INTERIOR OF THE DISTRIBUTION TUBE; AND (C) A RADIANT GRID CONFIGURED TO SURROUND SAID COMBUSTION ZONE AND ADAPTED TO BE HEATED BY BURNING OF THE FUEL-AIR MIXTURE THEREIN; (D) SAID ORIFICE STRUCTURE EXTENDING BEYOND THE FREE EDGES OF SAID OPPOSED FLANGES SO AS TO MAINTAIN SAID FREE EDGES OUT OF THE ZONE OF INTENSE COMBUSTION; (E) REFELCTORS HAVING SPACED LONGITUDINAL MOUNTING FLANGES ATTACHED TO THE OUTSIDE OF SAID OPPOSED FLANGES; (F) MEANS EXTENDING THROUGH ALL OF SAID FLANGES FOR SUPPORTING SAID ORIFICE STRUCTURE AND SAID REFLECTORS TO THE DISTRIBUTION TUBE; AND (G) MEANS FOR SUPPORTING SAID GRID FROM SAID REFLECTORS. 